It is known per se that the edge design of semiconductor components, particularly of power semiconductor components, has a considerable influence on the achievable blocking voltage strength of the component. Generally, the edge structures of semiconductor components can be divided into two main groups: edge structures in which an angle at which, for example, a p-n transition intersects the semiconductor surface is set on the semiconductor body by means of an edge chamfer, and edge structures with a plane semiconductor surface which are referred to as planar edge structures.
The edge chamfer in the edge region of the semiconductor component can be produced both mechanically, for example by grinding or lapping, and chemically by targeted etching. The angle of the edge chamfer is generally defined in relation to a transition from a semiconductor zone doped to a higher degree to one doped to a lesser degree, wherein this angle is referred to as a positive angle in the case in which the diameter of the semiconductor body decreases in the direction from the semiconductor zone doped to a higher degree to the semiconductor zone doped to a lesser degree, and otherwise as a negative angle.
In typical semiconductor components, particularly in disk cell diodes, a positive angle is usually provided as an edge termination. This angle causes a widening of the space-charge zone, so that the latter, given the dimensionings of the basic doping of an inner zone of the semiconductor body common today, abuts the heavily n-doped emitter already at relatively low applied blocking voltages. This results in excessive field strengths occurring in the region of the positive angle at the transition between lightly n-doped and the heavily n-doped area. These field peaks are critical particularly when, during a turn-off process with a high steepness of commutation, a high density of free electrons occurs at this location and locally divides the field curve. This can result in the failure of the semiconductor component. The angle range for a positive chamfer typically lies between about 25° to about 50°.
In particular, in semiconductor components with an edge chamfer with a positive angle, the anode surface at the side of the edge is larger compared to the cathode surface at the side of the edge, so that in the on-state an increased current density can occur at the edge of the semiconductor component on the side of the cathode. Since the stored charge is proportional to the current density, a dynamic avalanche will preferably occur in the region of the edge.
So far, it is provided as a countermeasure that a second edge chamfer with a shallower angle, particularly a shallow negative angle, is etched, in addition to the positive edge chamfer, into the semiconductor body, in the outer or edge region of the heavily n-doped emitter of the semiconductor component. This is usually done by means of spin etching. However, this is disadvantageous in that this method results in an edge contour that is difficult to reproduce, and thus in fluctuations of the electrical properties from component to component. In particular, components with local weak points, particularly excessive field strengths, at the above-mentioned location may sporadically occur.
Thus, a need exists for providing a semiconductor component in which excessive field strength peaks in the edge region, which occur during the turn-off process of the semiconductor component, are specifically avoided. Furthermore, the semiconductor components are supposed to be easier and more accurate to reproduce and have a lower level of fluctuation in the electrical properties, particularly during the turn-off or depletion phase of the semiconductor component.